We turn on the lights in our house from a desk in an office miles away. Our refrigerator alerts us to buy milk on the way home. A package of cookies on the supermarket shelf suggests that we buy it, based on past purchases. The cookies themselves are on the shelf because of a “smart” supply chain. When we get home, the thermostat has already adjusted the temperature so that it’s toasty or bracing, whichever we prefer. This is the Internet of Things—a networked world of connected devices, objects, and people.

Maps of physical spaces locate us in the world and help us navigate unfamiliar routes. Maps of topical spaces help us visualize the extent and structure of our collective knowledge; they reveal bursts of activity, pathways of ideas, and borders that beg to be crossed. This book, from the author of Atlas of Science, describes the power of topical maps, providing readers with principles for visualizing knowledge and offering as examples forty large-scale and more than 100 small-scale full-color maps.

Internet trolls live to upset as many people as possible, using all the technical and psychological tools at their disposal. They gleefully whip the media into a frenzy over a fake teen drug crisis; they post offensive messages on Facebook memorial pages, traumatizing grief-stricken friends and family; they use unabashedly racist language and images. They take pleasure in ruining a complete stranger’s day and find amusement in their victim’s anguish. In short, trolling is the obstacle to a kinder, gentler Internet.

In making decisions, we often seek advice. Online, we check Amazon recommendations, eBay vendors’ histories, TripAdvisor ratings, and even our elected representatives’ voting records. These online reputation systems serve as filters for information overload. In this book, experts discuss the benefits and risks of such online tools.

The vast majority of all email sent every day is spam, a variety of idiosyncratically spelled requests to provide account information, invitations to spend money on dubious products, and pleas to send cash overseas. Most of it is caught by filters before ever reaching an in-box. Where does it come from?

“Big Data” is on the covers of Science, Nature, the Economist, and Wired magazines, on the front pages of the Wall Street Journal and the New York Times. But despite the media hyperbole, as Christine Borgman points out in this examination of data and scholarly research, having the right data is usually better than having more data; little data can be just as valuable as big data. In many cases, there are no data—because relevant data don’t exist, cannot be found, or are not available.

Professional and amateur musicians alike use social media as a platform for showcasing and promoting their music. Social media evaluation practices—rating, ranking, voting, “liking,” and “friending” by ordinary users, peers, and critics—have become essential promotional tools for musicians. In this report, H. Cecilia Suhr examines one recent development in online music evaluation: the use of digital badges to aid in assessment and evaluation. Digital badges have emerged in recent years as a potential credentialing method in informal learning environments.

The United States ushered in a new era of small-scale broadcasting in 2000 when it began issuing low-power FM (LPFM) licenses for noncommercial radio stations around the country. Over the next decade, several hundred of these newly created low-wattage stations took to the airwaves. In Low Power to the People, Christina Dunbar-Hester describes the practices of an activist organization focused on LPFM during this era. Despite its origins as a pirate broadcasting collective, the group eventually shifted toward building and expanding regulatory access to new, licensed stations.

For decades, social movements vied for attention from the mainstream mass media—newspapers, radio, and television. Today, some say that social media power social movements, from Iran’s so-called “Twitter revolution” to the supposed beginnings of the Egyptian revolution on a Facebook page. Yet, as Sasha Costanza-Chock reports, activists and organizers agree that social media enhances, rather than replaces, face-to-face organizing. The revolution will be tweeted, but tweets alone do not the revolution make.